audio amplifier vs amplifier

audio amplifier and amplifier both are nouns.

Word	Noun	Adjective	Verb	Adverb
audio amplifier	Yes	No	No	No
amplifier	Yes	No	No	No

As nouns, amplifier is a hypernym of audio amplifier; that is, amplifier is a word with a broader meaning than audio amplifier:

audio amplifier: an amplifier that increases the amplitude of reproduced sound
amplifier: electronic equipment that increases strength of signals passing through it

audio amplifier (noun)	amplifier (noun)
an amplifier that increases the amplitude of reproduced sound	electronic equipment that increases strength of signals passing through it